U.S. patent number 11,264,053 [Application Number 17/216,017] was granted by the patent office on 2022-03-01 for heat-assisted recording head having sub wavelength mirror formed of first and second materials.
This patent grant is currently assigned to Seagate Technology LLC. The grantee listed for this patent is Seagate Technology LLC. Invention is credited to Weibin Chen, Michael Allen Seigler, Ruoxi Yang, Nan Zhou.
United States Patent |
11,264,053 |
Chen , et al. |
March 1, 2022 |
Heat-assisted recording head having sub wavelength mirror formed of
first and second materials
Abstract
A recording head has a near-field transducer proximate a
media-facing surface of the recording head. The near-field
transducer extends a first distance away from the media-facing
surface. A waveguide overlaps and delivers light to the near-field
transducer. Two subwavelength focusing mirrors are at an end of the
waveguide proximate the media-facing surface. The subwavelength
mirrors are on opposite crosstrack sides of the near-field
transducer and separated from each other by a crosstrack gap. The
subwavelength focusing mirrors each include a first material at the
media-facing surface and a liner that covers an edge of the
mirror.
Inventors: |
Chen; Weibin (Edina, MN),
Zhou; Nan (Chanhassen, MN), Yang; Ruoxi (Plymouth,
MN), Seigler; Michael Allen (Eden Prairie, MN) |
Applicant: |
Name |
City |
State |
Country |
Type |
Seagate Technology LLC |
Cupertino |
CA |
US |
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Assignee: |
Seagate Technology LLC
(Fremont, CA)
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Family
ID: |
75164357 |
Appl.
No.: |
17/216,017 |
Filed: |
March 29, 2021 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20210249039 A1 |
Aug 12, 2021 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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16855047 |
Apr 22, 2020 |
10964340 |
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62839863 |
Apr 29, 2019 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G11B
5/314 (20130101); G11B 5/6088 (20130101); G11B
5/4866 (20130101); G11B 5/39 (20130101); G11B
2005/0021 (20130101) |
Current International
Class: |
G11B
11/10 (20060101); G11B 5/48 (20060101); G11B
5/00 (20060101); G11B 5/39 (20060101); G11B
11/105 (20060101) |
Field of
Search: |
;360/59 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hindi; Nabil Z
Attorney, Agent or Firm: Mueting Raasch Group
Parent Case Text
RELATED PATENT APPLICATIONS
This application is a continuation of U.S. application Ser. No.
16/855,047 filed on Apr. 22, 2020, which claims the benefit of
Provisional Patent Application Ser. No. 62/839,863 filed on Apr.
29, 2019, both of which are hereby incorporated herein by reference
in their entireties.
Claims
What is claimed is:
1. A recording head comprising: a near-field transducer proximate a
media-facing surface of the recording head, the near-field
transducer extending a first distance away from the media-facing
surface; a waveguide that overlaps and delivers light to the
near-field transducer; and a pair of subwavelength focusing mirrors
at an end of the waveguide proximate the media-facing surface and
extending a second distance away from the media-facing surface that
is less than the first distance, the subwavelength mirrors on
opposite crosstrack sides of the near-field transducer and
separated from each other by a crosstrack gap, the subwavelength
focusing mirrors each comprising: a first material at the
media-facing surface; and a liner that covers an edge of the
subwavelength focusing mirror that faces the near-field transducer,
the liner formed of a plasmonic material, the first material more
mechanically robust than the plasmonic material.
2. The recording head of claim 1, wherein the crosstrack gap is
less than 300 nm.
3. The recording head of claim 2, wherein the crosstrack gap is
less than 100 nm.
4. The recording head of claim 1, wherein the first material
comprises one of Rh, Ir, Pt, Pd, Ru, or their alloys.
5. The recording head of claim 1, wherein the first material
comprises one of a ceramic material or a magnetic material.
6. The recording head of claim 1, wherein the plasmonic material
comprises one of Au, Ag, Cu, Al or their alloys.
7. The recording head of claim 1, wherein each subwavelength
focusing mirrors further comprises a second material stacked on the
first material, the second material facing away from the
media-facing surface, the liner covering the second material at the
edge of the subwavelength focusing mirror.
8. The recording head of claim 7, wherein the second material
comprises one of Au, Ag, Cu, Al or their alloys.
9. The recording head of claim 7, wherein the first material
protrudes further into the crosstrack gap than the second
material.
10. The recording head of claim 9, wherein the protrusion of the
first material into the crosstrack gap causes the subwavelength
focusing mirrors to function as optical side shields.
11. A recording head comprising: a near-field transducer proximate
a media-facing surface of the recording head; a waveguide that
overlaps and delivers light to the near-field transducer; and a
pair of subwavelength focusing mirrors at an end of the waveguide
proximate the media-facing, surface, the subwavelength mirrors on
opposite crosstrack sides of the near-field transducer and
separated from each other by a crosstrack gap, the subwavelength
focusing mirrors each comprising: a first material at the
media-facing surface that comprises one of Rh, Ir, Pt, Pd, Ru, or
their alloys; and a liner that covers the first material at an edge
of the subwavelength focusing mirror that faces the near-field
transducer, the liner formed of a different material than the first
material.
12. The recording head of claim 11, wherein the liner is formed of
a plasmonic material.
13. The recording head of claim 12, wherein the plasmonic material
comprises one of Au, Ag, Cu, Al or their alloys.
14. The recording head of claim 11, wherein the liner has a
thickness between about 1 nm to about 25 nm.
15. A recording head comprising: a near-field transducer proximate
a media-facing surface of the recording head and having a peg
extending towards the media-facing surface; a waveguide that
overlaps and delivers light to the near-field transducer; and a
pair of subwavelength focusing mirrors at an end of the waveguide
proximate the media-facing surface, the subwavelength mirrors on
opposite crosstrack sides of the near-field transducer and
separated from each other by a crosstrack gap, the subwavelength
focusing mirrors each comprising: a first material at the
media-facing surface; a liner that covers the first material at an
edge of the subwavelength focusing mirror that faces the near-field
transducer, the comprising a plasmonic material, the first material
being more mechanically robust than the plasmonic material; and a
protrusion that extends into the crosstrack gap towards the peg of
the near-field transducer, the protrusion having a downtrack
dimension that is less than that of the subwavelength focusing
mirror.
16. The recording head of claim 15, wherein a downtrack direction
of the protrusion is approximately equal to a corresponding
downtrack dimension of the peg of near-field transducer, the
protrusion being aligned with the peg of the near-field transducer
in a downtrack direction.
17. The recording head of claim 15, wherein a crosstrack opening
between the protrusions of the subwavelength focusing mirrors is
less than 300 nm.
18. The recording head of claim 17, wherein a crosstrack opening
between the protrusions of the subwavelength focusing mirrors is
less than 100 nm.
19. The recording head of claim 15, wherein the protrusions of the
subwavelength focusing mirrors function as optical side
shields.
20. The recording head of claim 15, wherein the first material
comprises one of Rh, Ir, Pt, Pd, Ru, or their alloys and the
plasmonic material comprises one of Au, Ag, Cu, Al or their alloys.
Description
SUMMARY
The present disclosure is directed to a heat-assisted recording
head having subwavelength mirror formed of first and second
materials. In various embodiments, a recording head has a
near-field transducer proximate a media-facing surface of the
recording head. The near-field transducer extends a first distance
away from the media-facing surface. A waveguide overlaps and
delivers light to the near-field transducer. Two subwavelength
focusing mirrors are at an end of the waveguide proximate the
media-facing surface and extend a second distance away from the
media-facing surface that is less than the first distance. The
subwavelength mirrors are on opposite crosstrack sides of the
near-field transducer and separated from each other by a crosstrack
gap. The subwavelength focusing mirrors each include a first
material at the media-facing surface and a liner covering the first
material at an edge of the subwavelength focusing mirror that faces
the near-field transducer. The first material is more mechanically
robust than a plasmonic material that forms the liner.
These and other features and aspects of various embodiments may be
understood in view of the following detailed discussion and
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The discussion below makes reference to the following figures,
wherein the same reference number may be used to identify the
similar/same component in multiple figures.
FIG. 1 is a perspective view of a slider assembly according to an
example embodiment;
FIG. 2 is a cross-sectional view of a slider along a down-track
plane according to according to an example embodiment;
FIG. 3 is a wafer plane view of a slider according to an example
embodiment;
FIGS. 4 and 5 are perspective and plan views of a subwavelength
mirror according to an example embodiment;
FIGS. 6 and 7 are sets of graphs showing simulation results of the
arrangement shown in FIGS. 4 and 5;
FIGS. 8 and 9 are perspective and plan views of a subwavelength
mirror according to another example embodiment;
FIGS. 10 and 11 are sets of graphs showing simulation results of
the arrangement shown in FIGS. 8 and 9;
FIG. 12 is a plan view of a subwavelength mirror according to
another example embodiment;
FIGS. 13-17 are perspective cutaway views of protrusions of a
subwavelength mirror according to various example embodiments;
and
FIG. 18 is a set of graphs comparing performance of the
subwavelength mirror embodiments shown in FIGS. 13-17.
DETAILED DESCRIPTION
The present disclosure is generally related to heat-assisted
magnetic recording (HAMR), also referred to as energy-assisted
magnetic recording (EAMR), thermally-assisted recording (TAR),
thermally-assisted magnetic recording (TAMR), etc. In a HAMR
device, a near-field transducer (NFT) concentrates optical energy
into a tiny optical spot in a recording layer, which raises the
media temperature locally, reducing the writing magnetic field
required for high-density recording. A waveguide delivers light to
the near-field transducer and excites the near-field
transducer.
One challenge in developing in HAMR products involves wear of the
optical components that can make impact life of the drives. One
cause for this is separation of parts and voiding within regions
surrounding the NFT. The optical components in this region are
subject to high temperatures and may become oxidized, which can
cause voiding or separation of some materials. A HAMR write
transducer described below uses a subwavelength mirror that
overlaps part of the NFT in an area near the air bearing surface
(ABS), which may also be referred to herein as a media-facing
surface. Generally, the subwavelength mirror has dimensions along
its reflecting surface that are smaller than the wavelength of the
incident light (e.g., 830 nm).
The subwavelength mirror focuses incident waveguide light onto the
NFT to assist waveguide-NFT coupling. The subwavelength mirror also
functions as an optical side shield to block background light.
Therefore, the laser current used for writing can be reduced and
thermal gradient improved. In order to obtain optimum optical
performance, the mirror is made from a material such as Au that is
a good optical and thermal characteristics. However, it has been
found that Au and similar plasmonic materials are subject to
degradation in the NFT region. Therefore, the present disclosure
describes to additional features to increase robustness and
durability of a subwavelength mirror.
In reference now to FIG. 1, a perspective view shows a read/write
head 100 according to an example embodiment. The read/write head
100 may be used in a magnetic data storage device, e.g., HAMR hard
disk drive. The read/write head 100 may also be referred to herein
interchangeably as a slider, head, write head, read head, recording
head, etc. The read/write head 100 has a slider body 102 with
read/write transducers 108 at a trailing edge 104 that are held
proximate to a surface of a magnetic recording medium (not shown),
e.g., a magnetic disk.
The illustrated read/write head 100 is configured as a HAMR device,
and so includes additional components that form a hot spot on the
recording medium near the read/write transducers 108. These HAMR
components include an energy source 106 (e.g., laser diode) and a
waveguide 110. The waveguide 110 delivers electromagnetic energy
from the energy source 106 to a near-field transducer (NFT) that is
part of the read/write transducers 108. The NFT achieves surface
plasmon resonance and directs the energy out of a media-facing
surface 112 to create a small hot spot in the recording medium.
In FIGS. 2 and 3, respective cross-sectional and wafer plane views
of the slider body 102 show a light delivery system according to an
example embodiment. The slider body includes an NFT 208, a magnetic
writer 210 and a micro-sized focusing mirror 212, referred to
herein as a subwavelength mirror, subwavelength focusing mirror,
subwavelength solid immersion mirror (SIM), mini-SIM, etc. Light,
emitting from the laser diode 106, is coupled into a
three-dimensional, single mode channel waveguide 110 by a waveguide
input coupler 206, which directs the light to a waveguide core 200.
The input coupler 206 is replaced by a bottom cladding layer 207
towards the media-facing surface 112. Note that other waveguide and
input coupler arrangements may be used with the NFT 208 and mirror
212.
The NFT 208 has an enlarged part with two curved ends 208a-b and a
protruded peg 208c. Other shapes may be possible for the enlarged
part of the NFT 208, e.g., rectangular, triangular. The NFT 208 is
placed proximate a side cladding layer 204 and top cladding layer
202 of the waveguide 110 and near the waveguide core 200. The NFT
208 could be also placed into the waveguide core 200. The NFT 208
achieves plasmonic resonance in response to the light coupled via
the waveguide 110, and creates a small hotspot 220 on a recording
medium 222 during recording.
A magnetic reader 224 is shown down-track from the NFT 208 and
writer 210. The magnetic reader 224 may include a magneto-resistive
stack that changes resistance in response to changes in magnetic
field detected from the recording medium 222. These changes in
magnetic field are converted to data by a read channel of the
apparatus (e.g., hard disk drive assembly).
As best seen in FIG. 3, the subwavelength mirror 212 includes
reflective metallic portions 212a-b on either crosstrack of the NFT
208. The mirror portions 212a-b focus the incident waveguide light
to the NFT 208 to assist in waveguide-NFT coupling. The mirror
portions 212a-b can also function as optical side shields that
block background light from exiting the media-facing surface 112.
The subwavelength mirrors described below utilize combinations of
soft plasmonic materials and hard materials that help improve
performance and life of the recording head 100.
In FIGS. 4 and 5, diagrams illustrate details of a subwavelength
mirror according to an example embodiment. The diagram in FIG. 4 is
a perspective view seen from the media-facing surface 112 and the
diagram in FIG. 5 is a plan view on a substrate-parallel plane. The
subwavelength mirror includes a pair of subwavelength focusing
mirrors 400 at an end of the waveguide 200 proximate the
media-facing surface 112. The subwavelength focusing mirrors 400
are on opposite crosstrack sides of the near-field transducer 208
and separated from each other by a crosstrack gap 404. The width of
crosstrack gap 404 may be less than a corresponding crosstrack
width 406 of the NFT 208. As seen in FIG. 5, the near-field
transducer 208 extends a first distance 500 away from the
media-facing surface 112 and the mirrors 400 extend a second
distance 502 away from the media-facing surface that is less than
the first distance 500. For example, the second distance 502 may be
less than half of the first distance 500.
Each of the subwavelength focusing mirrors includes a first
material 400a at the media-facing surface 112 and a second material
400b (e.g., a plasmonic material) facing away from the media facing
surface 112 and in contact with the first material 400a. In this
example, an interface 400d between the first and second materials
400a, 400b is parallel with the media facing surface 112. In other
embodiments, the interface between the first and second materials
400a, 400b may be at an angle to the media-facing surface 112. The
first material 400a is more mechanically robust than the second
material 400b. A liner 400c coats an edge of the subwavelength
focusing mirrors that faces the near-field transducer 208. As seen
here, the liner 400c covers both the first and second materials
400a, 400b and extends into the gap 404.
The second material 400b and liner 400c may include the same or
different material. The second material 400b (and optionally the
liner 400c) may be a plasmonic material with good optical
characteristics such as Au, Ag, Cu, Al or their alloys. In some
embodiments, the liner 400c can be made of hard material, such as
Rh, Ir, Pt, Pd, Ru, or their alloys. The hard, first material 400a
is presented at the media-facing surface 112 for ABS protection and
design robustness, and may include such materials as Rh, Ir, Pt,
Pd, Ru, or their alloys. The soft plasmonic materials 400b, 400c
are inside the media-facing surface 112 for better optical coupling
and thermal conduction. The liner thickness 402 may be from 1 nm to
25 nm.
In FIGS. 6 and 7, a set of graphs show results of an analysis
performed on the mirror arrangement shown in FIGS. 4 and 5 with a
liner 400c formed of a soft plasmonic material, Au, Ag, Cu, Al or
their alloys. There is a slight drop in thermal gradient (TG) with
thicker soft plasmonic liner. The NFT temperature (NFT .DELTA.T)
and mirror temperatures (mSIM .DELTA.T) drop with a thicker soft
plasmonic liner 400c. The liner thickness 402 has little impact on
laser current (Ieff). In FIG. 7, a set of graphs show an analysis
performed on the mirror arrangement shown in FIGS. 4 and 5 with a
liner 400c formed of a hard material, such as Rh, Ir, Pt, Pd, Ru,
or their alloys. The NFT and mirror temperatures go up with thicker
hard material liner 400c, as does the required laser current.
Though the temperature is higher in this case, this design may have
better robustness than one with a softer plasmonic material liner
400c.
In FIGS. 8 and 9, diagrams illustrate details of a subwavelength
mirror according to another example embodiment. The diagram in FIG.
8 is a perspective view seen from the media-facing surface 112 and
the diagram in FIG. 9 is a plan view on a substrate-parallel plane.
The subwavelength mirror includes a pair of subwavelength focusing
mirrors 800 at an end of the waveguide 200 proximate the
media-facing surface 112. Each of the subwavelength focusing
mirrors includes a first material 800a at the media-facing surface
112 and a second material 800b facing away from the media facing
surface and in contact with the first material 800a. The first
material 800a is more mechanically robust than the second material
800b. This embodiment has no liner comparable to what is shown in
FIGS. 4 and 5.
The second material 800b may include a plasmonic material with good
optical characteristics such as Au, Ag, Cu, Al or their alloys. The
hard, first material 800a is presented at the media-facing surface
112 for ABS protection and design robustness, and may include such
materials as Rh, Ir, Pt, Pd, Ru, or their alloys. In other
embodiments, the first material 800a may be ceramic materials as
ZrN, TiN, etc., or a magnetic material such as Fe, Ni, NiFe, FeCo,
or alloys thereof. The soft plasmonic material 800b is inside the
media-facing surface 112 for better optical coupling and thermal
conduction.
One parameter that can affect performance of this and other
embodiments is the crosstrack gap 802 opening between the mirrors
800. In FIG. 10, a set of graphs show results of a simulation using
various values of the gap 802 (labeled "SIM opening" in the
graphs). These graphs generally show a higher downtrack thermal
gradient (DTTG) with a narrower opening. The NFT and mirror
temperature will increase if that gap 802 is too small, and laser
current will also increase for a smaller gap 802. These gap
dimensions may also be used for embodiments with a liner as shown
in FIGS. 4 and 5, as well as embodiments described below.
Another parameter that can affect performance of this and other
embodiments is the height 900 of the second material 800b as it
extends away from the media-facing surface as shown in FIG. 9. In
FIGS. 10 and 11, a set of graphs show results of a simulation using
various values of the height 900. Higher NFT and mirror
temperatures are seen with larger height 900, and laser current
will also increase with larger height 900. Thermal gradient is not
particularly sensitive to the height 900. These height dimensions
may also be used for embodiments with a liner as shown in FIGS. 4
and 5, as well as embodiments described below.
In FIG. 12, a diagram illustrates details of a subwavelength mirror
according to another example embodiment. In this example,
subwavelength focusing mirrors 1200 are at an end of the waveguide
200 proximate the media-facing surface 112 and separated from each
other by a crosstrack gap 1202. Each of the subwavelength focusing
mirrors 1200 includes a first material 1200a at the media-facing
surface 112 and a second material 1200b facing away from the media
facing surface and in contact with the first material 1200a. The
first material 1200a is more mechanically robust than the second
material 1200b, and may include any of the mechanically robust
materials described above. Similarly, the second material 1200b may
include any of the plasmonic materials described above.
In this embodiment, the first material 1200a protrudes into the gap
1202 further than the second material 1200b. This results in a
discontinuity 1200c (e.g., a non-smooth transition) in edges of the
mirrors that face the NFT 208. In this way, the protrusion of the
first material 1200a acts as an optical side shield. By extending
the first material 1200a this way, the gap 1202 can be decreased to
less than 100 nm, or even less than 50 nm. As indicated by dashed
lines 1204, a liner as shown in FIGS. 4 and 5 may optionally be
used with this embodiment.
In FIGS. 13-17, perspective cutaway views show various optical side
shield embodiments according to various embodiments. In each of
these figures, side shields are extensions from first material
parts 1300, 1400, 1500, 1600, 1700 of a mirror that is joined to a
second material part 1300, the second material part being formed of
any plasmonic materials as described above. For all of these
embodiments, a recording head would include a mirror-image first
and second material parts on an opposing crosstrack side of the NFT
208 separated by a gap 1304. The first material parts 1300, 1400,
1500, 1600, 1700 may be made from any robust, hard material as
described above. All of these embodiments may be used with a liner
as shown in FIGS. 4 and 5.
In FIG. 13, a first material part 1302 has a protrusion 1302a that
extends into an inter-mirror gap 1304 in the crosstrack direction.
The downtrack dimension of the protrusion 1302a matches that of the
NFT peg 208c and is aligned with the peg 208c in the downtrack
direction. In FIG. 14, a first material part 1400 has a protrusion
1400a that extends into the inter-mirror gap 1304. The downtrack
dimension of the protrusion 1400a nearly matches that of the entire
NFT 208 and is roughly aligned with the NFT 208 in the downtrack
direction. The protrusion 1400a does not quite extend to the
waveguide core 200 in the downtrack direction, as indicated by gap
1402.
In FIG. 15, a first material part 1500 has a protrusion 1500a that
extends into the inter-mirror gap 1304. The downtrack dimension of
the protrusion 1500a matches that of both the NFT 208 and waveguide
core 200, such that the protrusion extends into the waveguide core
200. In FIG. 16, a first material part 1600 has a protrusion 1600a
that extends into the inter-mirror gap 1304. The downtrack
dimension of the protrusion 1600a extends into and matches that the
waveguide core 200 only, with which it is aligned in the downtrack
direction. In FIG. 17, a first material part 1700 has a protrusion
1700a that extends into the inter-mirror gap 1704. The protrusion
1700a extends the full length of the mirror portion in the
downtrack direction, matching a downtrack dimension of the first
material part 1300.
In FIG. 18, graphs 1800-1802 show analyses of the different
protrusion designs in FIGS. 13-17, as well as a non-protruding
design as shown in FIG. 8. For these analyses, the NFT temperature,
downtrack TG, and laser current were determined for different ABS
opening sizes, which here refer to the minimum crosstrack distances
between opposing protrusions on either side of the gap 1304. Note
that in graph 1802, only the minimum and maximum current curves are
labeled for purposes of maintaining clarity in the drawing. With
design having a protrusion that matches the NFT sides and waveguide
as shown in FIG. 15, TG is same as full protrusion shown in FIG.
17. The NFT Temperature can be 20-30K lower with a protrusion that
matches the NFT sides and waveguide as shown in FIG. 15.
Unless otherwise indicated, all numbers expressing feature sizes,
amounts, and physical properties used in the specification and
claims are to be understood as being modified in all instances by
the term "about." Accordingly, unless indicated to the contrary,
the numerical parameters set forth in the foregoing specification
and attached claims are approximations that can vary depending upon
the desired properties sought to be obtained by those skilled in
the art utilizing the teachings disclosed herein. The use of
numerical ranges by endpoints includes all numbers within that
range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and
any range within that range.
The foregoing description of the example embodiments has been
presented for the purposes of illustration and description. It is
not intended to be exhaustive or to limit the embodiments to the
precise form disclosed. Many modifications and variations are
possible in light of the above teaching. Any or all features of the
disclosed embodiments can be applied individually or in any
combination are not meant to be limiting, but purely illustrative.
It is intended that the scope of the invention be limited not with
this detailed description, but rather determined by the claims
appended hereto.
* * * * *